Draw bending apparatus



1962 F. J. FUCHS, JR

DRAW BENDING APPARATUS 5 Sheets-Sheet 1 Filed Oct. 21. 1958 INVENTORATTORNEY F. J. FUCHS, JR

DRAW BENDING APPARATUS Nov. 20, 1962 5 Sheets-Sheet 2 Filed 001.. 21,1958 INVENTOR ATTORNEY Nov. 20, 1962 F. J. FUCHS, JR

DRAW BENDING APPARATUS 5 Sheets-Sheet 3 Filed Oct. 21, 1958 INVENTOR s,J11,

ATTORNEY Nov. 20, 1962 F. J. FUCHS, JR 3,064,711

DRAW BENDING APPARATUS Filed 001;. 21, 1958 5 Sheets-Sheet 4 Fzwwz's(Irma/2. .177;

BY 6/1. W

ATTORNEY Nov. 20, 1962 F. J. FUCHS, JR

DRAW BENDING APPARATUS 5 Sheets-Sheet 5 gm. riff MMH Filed 061.. 21.1958 INVENTOR lr'awa'a (lllw ATToRzllEY v rates This invention relatesto draw bending apparatus and more particularly to draw bendingapparatus having a servo-controlled system for correlating the travel ofa tube-advancing booster with the amount of rotation of a bending form.

Tube bending machines generally of the nature of the present inventionare used extensively in the manufacture of tubular products such astubular chair frames, bicycle frames, towel bars, and the like. Thesebending machines are successful in the rapid and accurate bending oftubular stock to be assembled into products as aforementioned; however,conventional bending machines are incapable of controlling withexactness the extent to which tubular walls are stretched and compressedduring the draw bending operation.

The effect of the drawing operation on the thickness of tubular walls atthe area of bend is a significant factor in instances where the insidedimensions of a tube must be maintained uniformly throughout the lengthof the tube, as, for example, in wave guide tubing. Also, thelightweight tubing employed customarily in the fabrication of waveguides, or the like, is relatively thin-walled and ductile; hence,bending of such tubing must be made without an appreciable weakening ofthe walls due to the stretching thereof.

Conventional draw bending machines generally are composed of a rotatablebending form, a mandrel, a clamp die rotatable with the bending form forconstraining a tube mounted over the mandrel against the bending form, apressure die and a wiper die for firmly guiding the tube to preventdistortion and wrinkling while the tube is being drawn by the bendingform. These machines in the past have been modified by the use ofchains, springs, pulley and belt combinations, or the like, to feed atube toward a bending form with the speed at which the tube is drawn bythe rotatable bending form in order to offset any undue stress placed onthe tube walls by reason of the formation of the bend.

An example of an improved draw bending machine is disclosed and claimedin my Patent 2,837,137, of June 3, 1958, entitled, Boosting Mechanismfor Bending Wave Guide Tubing with Controlled Neutral Axis. In thispatent a mechanical booster head for advancing a tube by action of anextensible cross arm moves a predetermined distance proportional to theangular distance which a bending form rotates for a given radius ofbend. By this arrangement there is effected a correlation betweentensional force occasioned in drawing a tube with compressional forcebrought against the rearward extremity of the tube being bent.

The neutral axis of the tube, which is the hypothetical dividing linebetween compressional and tensional forces on a tube, is controlledthrough the correlation of tensional and compressional forces mentioned.By moving the neutral axis outwardly from the tube centerline toward theouter wall of the tube, the degree of thinning of that wall iscontrolled to prevent rupture of the wall by the deleterious tensionalstress normally introduced in the outer bend in such operations. Also,the inner wall of the tube, the wall clamped against the bending form,is thickened only to a controlled degree.

It is an object of this invention to provide new and improved drawbending apparatus.

It is another object of the present invention to provide Bfit'idfiiiPatented Nov. 29, 1952 a new and improved draw bending machine having aservo-controlled system for correlating the travel of a tube advancingbooster with the amount of rotation of a bending form.

Still another object of this invention is to provide mechanism forcontrolling the advance of a tube toward a bending form continuouslythroughout the drawing of a straight tube into a bent tube wherebyfluctuations in the desired correlation between-the rate of travel of atube-advancing booster and the rotation of a bending form arecompensated automatically.

Illustrative of the above objects, apparatus exemplifying certainfeatures of the invention may include a rotatable bending form forbending a tube, drive means coupled to the form for rotating the form,booster means engageable with a tube for applying pressure on the tubetoward the bending form, power means for moving the booster means, andmeans connected opcratively to the drive means, the power means, and tothe booster means for correlating automatically the rate of rotation ofthe bending form with the rate of advance of the tube by the boostermeans.

A complete understanding of the invention may be had from the followingdetailed description of a specific embodiment thereof when read inconjunction with the appended drawings wherein:

FIG. 1 is a perspective view of apparatus forming a preferred embodimentof the invention with parts thereof broken away for clarity;

FIG. 2 shows a plan view of the apparatus with parts thereof brokenaway;

FIG. 3 illustrates a side elevation of the apparatus shown in FIG. 2with parts thereof broken away;

FIG. 4 is an enlarged fragmentary plan view of a pivot assembly formingpart of the apparatus shown in FIGS. 2 and 3;

FIG. 5 illustrates a fragmentary vertical section of the pivot assemblytaken on lines 5-5 of FIG. 4 looking in the direction of the arrows;

FIG. 6 is a fragmentary vertical section of the pivot assembly taken onlines 6-6 of FIG. 4 looking in the direction of the arrows;

FIG. 7 is a fragmentary vertical section of the pivot assembly taken onlines 7-7 of FIG. 4 looking in the direction of the arrows;

FIG. 8 is a fragmentary vertical section taken on lines 8-8 of FIG. 4looking in the direction of the arrows illustrating the mounting of thepivot assembly on a support ring;

FIG. 9 is a fragmentary vertical section taken on lines 9-9 of FIG. 4looking in the direction of the arrows showing the connection betweenelements of the pivot assembly;

FIG. 10 is a plan view of a circular plate of the pivot assembly shownin FIG. 4;

FIG. 11 is a perspective view of the circular plate shown in FIG. 10;

FIG. 12 shows a perspective view of an upper control rod plate of thepivot assembly shown in FIG. 4;

FIG. 13 is a perspective view of a lower control rod plate of the pivotassembly shown in FIG. 4;

FIG. 14 illustrates in perspective view a bearing ring forming anelement of the pivot assembly;

FIG. 15 is a perspective view, partly broken away, of an upper controlrod of the pivot assembly shown in FIG. 4;

FIG. 16 shows an enlarged perspective view, partly broken away, of alower control rod of the pivot assembly;

FIG. 17 is an enlarged view of a pin assembly, partly in section,mounted upon a booster rod;

FIG. 18 is an enlarged vertical sectional view of a servo-valve designedto control the automatic operation of power-actuated members of theapparatus;

(FIG. 19 is a schematic diagram of a hydraulic system of the apparatus;

FIG. 20 is a schematic diagram of the pivot assembly positioned inrelation to a bending form and a booster means;

FIG. 21 illustrates an alternative embodiment of an element of theapparatus; and

FIG. 22 is a modification of the upper control rod of the apparatusshown in vertical sectional view taken on lines 22- 22 of FIG. 21.

Referring now to the drawings wherein like reference charactersdesignate like or corresponding parts throughout the several views,there is shown in FIGS. 1, 2, and 3, a machine 23 for draw bendingtubing which may be, for example, rectangular wave guide tubing. Themachine 23 includes a frame 24 with a top plate 25 and a lowerhorizontally-disposed shelf plate 26, onto which plates are assembledthe novel components appurtenant to the machine.

The draw bending machine 23 includes a booster assembly 27 which ismounted on the top plate 25 for movement laterally of the longitudinalcenterline of the machine, a pivot assembly 28 positioned intermediatethe end portion of the top plate 25 and positioned substantially on thelongitudinal centerline of the machine, and a rotatable bending formassembly 29 located on the machine top plate 25 with its center ofrotation positioned substantially on the longitudinal centerline of themachine 23 at the end of the machine opposite the location of thebooster assembly 27. A bending form drive assembly 31, and a hydraulicsystem 32 (FIG. 19) for actuation of the operative elements of theassemblies, is supported, for example, on the shelf plate 26.

The booster assembly 27 includes in general three hydraulic cylinders33, 34, and 35, the latter being a mandrel cylinder for advancing amandrel rod 36 into contacting engagement with the interior of a tube 37which is to be draw bent by the bending form assembly 29. The cylinders33, 34, and 35 .are mounted on a common support 38 which is providedwith a lower lip portion 39 slidably receivable in a guideway 41 of aguide bar 42. A slotted portion 43 of the support 38 is mounted slidablyon an elongated block 44 of the machine top plate 25. Accordingly, thebooster assembly 27 may be moved laterally with respect to thelongitudinal centerline of the machine 7 frame 24.

Horizontally spaced apart from the mandrel cylinder 35 and adjacent eachside thereof are positioned hydraulic booster rod cylinders 33 and 34which are coupled together cooperatively at their forward'ends by meansof a yoke 45. The arms of the yoke 45 are connected rigidly to thepiston rods of the respective booster rod cylinders 33, 34 forsimultaneous reciprocable movethereof for application of pressureagainst the trailing edge of the tube 37. A'conventional threadedsleeve-coupling 49 is provided for attachment of the extension booster'rod'47 onto thebooster rod 46. As best shown in FIG. 1, the booster rod46 is a hollow sleeve which receives coaxially the mandrel rod 36 forinsertion into the tube 37 to support the walls thereof against collapseduring the bending operation.

The bending form assembly 29, FIG.1, is of a conventional design andmayinclude a bending form 51 to which is clamped the tube 37 by means of aclamp die 52 mounted on a carriage 53 for lateral adjustment. A pressuredie 54 and a wiper die 55 are spaced apart horizontally to receive thetube 37 therebetween for guidance into proper alignment for draw bendingby the bending form 51. When thus positioned, the tube 37 is advanced bythe drawing action of the bending form 51 on the forward end of the tube37 held against the form 51 by the clamp die 52, and by the pressureexerted against the trailing edge of the tube 37 by the booster element48.

For rotating the bending forrn51 the drive assembly 31 includes abending form sprocket 56 which is keyed for rotation on an axle 57 whichin turn intersects perpendicularly the longitudinal centerline of themachine. The axle 57 passes through a vertically extending passage.

in the bending form 51 and is secured thereto by a suit able fastenersuch as nut 58. By this arrangement any angular movement of the sprocket56 is imparted equally and simultaneously to the bending form 51.

A roller chain 59 is entrained about the bending form sprocket 56, oneend of the chain 59 being engaged fixedly by means such as a clevismounting, not shown, to a piston rod 61 of a double-acting hydraulicdrive cylinder 62. The cylinder 62 is secured in position by suitablemeans such as brackets 63 fastened to the shelf plate 26 of the machine23. The other end of the-roller chain 59 is engaged fixedly by suitablemeans (not shown) to a slide block 64. The Slide block 64 is connectedto the piston rod 61 of the double-acting hydraulic drive cylinder 62and is supported for axially slidable movement within a groove providedin support 60 fastened on the side wall of machine 23.

At the end of the machine remote from the location of the drive sprocket56, FIG. 1, the roller chain 59 is passed around an idler sprocket 65which is located preferably within the machine frame 24 beneath thebooster assembly 27. The idler sprocket 65 is fastened to the shelfplate 26 for rotation about a vertical axis which intersects and isnormal to the longitudinal centerline of the machine in a plane parallelto the top plate 25 and normal to a plane which includes the bendingform sprocket 56, the roller chain 59, and the piston rod 61 of thehydraulic drive cylinder v62. Upon the controlled application of fluidpressure into the hydraulic drive cylinder 62, the chain 59 may beadvanced by the piston rod 61 either to rotate the bending form 51counterclockwise, or withdrawn to rotate the bending form 51 clockwise.

An arm 66 of the pivot assembly 28 is coupled pivot.- ally at one end tothe slide block 64 (FIGS. 1, 2, and 3) by a pivot stud 67. The arm 66 iscomposed of a lower control rod 6Sand an upper-control rod 69. Rods 68and 69 are assembled together in a vertically spaced relationship alongparallel longitudinal axes by means of a lower control rod plate 71 andan upper control rod plate 72. Referring to FIGS. 4 through 14,.thespecific structure of the pivot assembly 28 is shown from anassembled to a completely unassembled condition.

The entire pivot assembly 28, FIG. 4, is contained by a support ring 73and is mounted within an aperture ,74 formed through the top plate 25 ofthe machine frame 24. The assembly 28 is positioned for rotation aboutan axis which is normal to the longitudinal center-line of the machine.A bearing 75 is force-fitted, for example, in an abutting concentricposition with respect to the support ring 73 and is provided with aninner circumferential projection 76 adapted to support pivotally twocircular plates 77, each having an L-shaped outer periphery in crosssection, FIGS. 10 and 11. The circular plates 77 are stacked one on theother to form a U-shaped mating surface for surrounding frictionalengagement with the bearing 75 at its inner periphery and, inparticular, about the projection 76 thereon. When the plates 77 areplaced together in stacked fashion, machined slots 78 form recesses intowhich are mounted ball bearings 79 on means such as dowels 81. Thecircularplates 77 are fastened together by screws, or the like, whichmay be engaged threadedly into vertically aligned holes 82 in each ofthe respective plates 77, FIGS. and 11. Also, an elongated aperture 83is formed centrally through each circular plate 77 and arranged to be invertical alignment with the companion aperture of its matching plate 77when the plates are finally assembled.

The upper control rod plate 72 and the lower control rod plate 71, shownin detail in FIGS. 4 through 9, are of the same rectangularconfiguration. The upper plate 72 is provided with a longitudinallyextending slot 84 into which is received fixedly the upper control rod69. Also, the lower plate 71 has similar slots 84, one for receiving theupper control rod 69 and another for receiving slidably the lowercontrol rod 68 such that the lower control rod 68 may vary in lengthbetween the pivot stud 67 and the pivot assembly 28 as necessary whenthe arm 66 pivots.

The upper control rod plate 72 is formed with an elongated aperture 85which corresponds in configuration with the apertures 83 provided in thecircular plates 77. An upstanding central body portion 86 of the lowercontrol rod plate 71, best shown in FIG. 13, is designed to be receivedthrough the apertures 83, and 85, for connection to the upper controlrod 69. In this manner a rigid coupling between the lower control rod 68and the upper control rod 69 is effected. By reference to FIG. 4, it maybe understood readily that the upper control rod plate 72 overlies boththe circular plates 77 and a portion of the support ring 73. The lowercontrol rod plate 71 underlies the same relative elements as does plate72, FIGS. 7 and 8.

The lower and the upper control rod plates 71 and 72 are each providedwith side slots 87 to receive roller bearings 88 mounted on dowels 89.The roller bearings 88 of the plates 71 and 72 contact the support ring73 on its opposite horizontal faces to enable a substantiallyfrictionless translatory action to exist between these elements.

The upstanding central body portion 86 of the lower control rod plate 71has a width slightly less than the width of the apertures 83 throughwhich it is received slidably. By the axial length of each of theelongated apertures 83 being greater than the axial length of thecentral body portion 86 translatory movement of the body portion 86 ispossible, through contact with the bearings 79, in a direction withinthe confines of the apertures 83 perpendicular to the axis of the arm66. It is apparent therefore that the pivot assembly arm 66 moves notonly in an angular pivotal path in bearing 75 about an axis of rotationnormal to the plane which includes the machine top plate 25, but also ina path perpendicular to the axis of the arm 66 within the apertures 83.

A cam roller 91 is supported by the lower control rod plate 71 by abracket 92 fixed to a cover plate 93. As shown in FIG. 5, the cam roller91 is designed to contact operatively a servo-valve plunger 94 having aconical head, the centerline of which is coincident with the center ofthe support ring 73. The cam roller 91 moves with any translatorymovement of the pivot assembly 28, and the plunger 94 is caused by suchmovement of the cam roller 91 to reciprocate in a vertical path wherebya spool 95, contained within a servo-valve 96, FIG. 18, is actuated.

A booster pin subassembly 97 is clamped removably at a preferredlocation on the booster rod 46, as shown in FIG. 17. A booster pin 98,carried by a pin housing 99, is designed to be adjustable laterally withrespect to the longitudinal centerline of the machine 23 by theincorporation of a slide 108. A pressure spring 181 normally urges thepin 98 to project downwardly beyond the limits of the pin housing 99.The spring-biased pin 98 is designed to contact frictionally an inclinedsurface 102 of the upper control rod 69, FIG. 15, and, during normalbending operation of the machine 23, brings pressure to bear against avertical step 103 formed on the upper control rod 69.

Referring to FIG. 18, wherein the servo-valve 96 is shown incross-sectional view, the valve plunger 94 is positioned normally inuppermost vertical extension by means of a compression spring 186positioned suitably within a passage 107 of the valve body 188. Thevalve plunger 94 is formed integrally, for example, with the elongatedspool which is provided with circular lands 189 and grooves 111. Thelands 109 are of a thickness to close and to open effectively ports Athrough I which are drilled through the valve body 168. Counterbores 112are provided for each port and are threaded to enable the coupling of aconventional hydraulic conduit fitting thereto. The sequence ofoperation of the servovalve 96 is best explained in conjunction with thedetailed description of the hydraulic pressure system, FIG. 19.

Operation The tube 37 is clamped into position against the bending form51, as shown in FIG. 1, by the clamp die 52, and guided by the pressuredie 54 and the wiper die 55 which are forced into frictional contactwith the tube 37 by fluid-operated means, not shown. The booster rod 46and mandrel rod 36 are aligned with the centerline of the clamped tubing37, and the pin subasscmbly 97 is fastened onto the rod 46 at apreferred location for preloading force against the rear of the tube 37before the actual bending of the tube is started. Then the pin 98 isadjusted by means of a conventional dovetail slide 108- so as to lie onthe desired neutral axis of the tube 37. The hydraulic system 32, FIG.19, is furnished fluid under pressure by suitable pump means 113 whichis in communication with a reservoir 144, and, through the operation ofa four-way valve 115, the fluid may be introduced selectively into orexhausted from the system 32 at points 116 and 117.

To perform a bending cycle, fluid is introduced into the system 32 atpoint 116 into line 118, one branch of which leads to the rear of themandrel cylinder 35. A sequence valve 119 is placed in line 118 to opena line 121 upon a predetermined threshold pressure being reached. Thispressure is determined by the desired extent of advancement of themandrel rod 36 toward the tube 37 The fluid is ported via the sequencevalve 119 through the line 121 into the servo-valve 96 at port D, and,since at this stage the spool 95 of valve 96 is not depressed byoperation of cam roller 91 on the valve plunger 94, the port A is opento receive the fluid flowing into port D. From port A the fluid is ledthrough conduit 122 to the rear of the booster rod cylinders 33 and 34.

At this stage of the bending operation the booster rod 46 advancestoward the bending form assembly 29, preloading pressure through thebooster element 48 onto the rear of the tube 37. By means of suchpreloading the metal of the tube 37 is compressed at the area of theproposed bend in order to anticipate the rotation of the bending form51. Thus, when the bending form 51 is caused to rotate and draw the tube37, a predetermined amount of metal is forced into the outer and innerwalls of the tube 37 at the area of the bend from the start of theoperation.

When the pin 98 of the booster pin subassembly 97 strikes the verticalstep 103 on the upper control rod 69, the pivot assembly 28 shiftswithin the apertures 83- 83 in a manner as explained hereinbefore. Thecam roller 91 moves with the pivot arm 66 when the pivot assemblyshifts, depressing the plunger 94 of the servovalve '96 to a neutralposition, as shown in PEG. 18. As the plunger 94 is being depressed, thespool 95 is moved downwardly to open port G to port F.

The drive cylinder 62 is actuated when ports F and G are open to conductfluid from the reservoir 114 to port G, thence through a pipe 124, tothe cylinder 62. During the period of the actuation of the cylinder 62,the port A, FIG. 18, is closed so as to cut ofi the supply of fluid tothe booster rod cylinders 33 and 34, thus stopping the advancement ofthe booster rod 46 with the booster pin 7 subassembly 97. Fluid from theforward end of the drive cylinder 62 is exhausted through the line 125to port H of the servo-valve to port I, and thence to the reservoir 114.V

Inasmuch as the roller chain 59 is connected to the slide block 64 andthe arm 66 of the pivot assembly 28, the upper control rod 69 pivotallymoves away from the pin 98 of the booster pin subassembly 97, and thisin turn enables the spool 95 to rise within the servo-valve 96. Thespool-up positioning of the spool 95 attained in this fashion graduallycloses port G to stop fluid flow to the drive cylinder 62, and reopensport A to port D. Thus, the booster cylinders 33 and 34 again advancethe booster rod 46 with 'the booster pin subassembly 97 toward thebending form assembly 29 and the pin 98 strikes the step 103 of rod 69to repeat the performance which is stimulated by the movement of theservo-valve spool 95.

If the force exerted by the pin 98 on the rod 69 exceeds a determinedamount, the spool 95 is depressed by the cam roller 91 to cause spool 95to open port B to port D so as to introduce fluid to the forward end ofthe booster cylinders 32 and 33 via line 127. This action reverses thedirection of travel of the booster rod 46, and fluid from the rearportion of these cylinders is dumped through the conduit 122 to port A,to port E, and through the line 128 to the reservoir 114. In thisspooldown situation the bending form 51 continues rotating by reason ofthe fluid fed to drive cylinder 62 via ports G and F as above discussed.

In practice a suitable design for the servo-valve 96 is a spool havingan upward movement from a neutral position (FIG. 18) of .060 inch, and aport C opening of .030 inch measured vertically. With this design thespool opposite port G closes this port if the spool moves upwardly .030inch or more. This action stops rotation of the bending form '51. As thearm 66 moves from contact with the pin 98, the spool 95 rises to openport A thus porting fluid to the booster cylinders 32 and 33. Thesecylinders are furnished fluid at the same time the drive cylinder 62 isfed until the spool 95 moves upwardly from the position shown in FIG. 18a distance of .030 inch to close completely the port G. By the provisionof such a servo-valve design, an accuracy of :.015 inch is possiblebetween the travel of the booster rod 46 and the rotation of the bendingform 51.

The bending cycle is completed when, for example, a rod 110 attached tothe slide block 64 trips a microswitch, not shown, to stop the action ofthe pump means 113. The four-way valve 115 is then caused, in eflect, toreverse the input and output points 116 and 117, respectively, of thehydraulic system 32. Thus, when the pump means 113 again is madeoperative, the fluid under pressure enters point 117 into the hydraulicsystem 32 through line 129. A pressure valve 131, situated in line 122,is designed to open when fluid is introduced through a pilot line 132,such that the servo-valve 96 is by-passed during the reversingoperation. The reversing fluid is fed through lines 129, 133', and 127into the forward portion of the booster cylinders 33 and 34 to withdrawthe booster rod 46. The exhaust from the rear of these cylinders isthrough line 122 to the pressure valve 131 which now has a port open tothe reservoir line 126 by action of the fluid fed to the valve 131through the pilot line 132'.

The action of the mandrel cylinder '35 is reversed when fluid throughline 133 is fed into the forward portion of the cylinder 35, and fluidis exhausted via line 118, through sequence valve 119, and to thereservoir 114. By separate hydraulic means, not shown, the bending formassembly 29 is returned to a starting position, and dies 52, 54, and 55are released from engagement with the tube 37. Suitable pressure reliefvalves 134 are provided in the system 32 in communication with thereservoir 114 via line 135.

To recapitulate, the action of the servo-valve 96 is as follows:

(1) in spool-up position, (a) Port J is closed;

(11) Port H is open only to port G; (0) Port F is open (always open);(at) Port I is open;

(e) Port B is open to port C;

(1) Port C is open;

(g) Port D is open (always open);

(h) Port A is open to port D;

(i) Port E is open (always open); (2) in spool-neutral position, FIG.18, (a) Port A is closed .to port D;

(b) Port D is open (always open);

(0) Port E is open (always open);

(d) Port B is closed;

(e) Port G is open (always open);

(f) Port I is closed;

(g) Port G is open to port F;

(11) Port F is open (always open);

(i) Port H is open (always open);

(j) Port J is open to port H;

and

(3) when the spool is in spool-down position,

(a) Port I is open to portI-I;

(b) Port H is open (always open);

(c) Port G is open to port F;

(d) Port F is open (always open);

(e) Port I is closed;

(f) Port C is closed;

(g) Port B is open to port D;

([1) Port D is open (always open);

(i) Port A is open to port F;

(j) Port E is open.

A second embodiment of the apparatus includes an upper control rod 169having a clamp 104, FIGS. 21 and 22, a cam surface 105 for engagementwith the booster pin 98, positionable selectively along the length ofthe rod 69. By the utilization of the clamp 104 a predetermined variancein the correlation of the speed of rotation of the bending form 51 andthe travel of the booster rod 46 is effected. For example, in theinstance of the cam design shown, the relatively straight portion 105enables a steady advance of the tube 37, whereas portion 105a causes afast advance of the tube 37 as generally possible at the beginning ofthe bending operation on the tube 37. The steady advance is desirableafter a tube has been work-hardened by the initial bending of a tubesuch that metal flow is retarded.

Theory of Operation Referring now to FIG. 20, for preloading apredetermined pressure onto the tube 37 before the bending form 51 iscaused to draw the tube 37, the booster pin subassembly 97 is stationeda distance Y on the booster rod 46 from the step 103 of the arm 66. Ashereinbefore explained, when the pin 98 of the booster pin subassembly97 urges the upper control rod 69 toward the bending form 51, the spoolof the servo-valve 96 is depressed to deprive the booster cylinders 33and 34 of their source of fluid, thus stopping the advancement of thebooster rod 46. The drive cylinder 62 then is fed fluid to drive theroller chain 59 and, consequently, the bending form 51 rotates.

The are C described by rotation of the bending form 51 for a bend ofangle on is equal to and to the distance X, where r is the radiusmeasured from the center of rotation of the bending form to the desiredneutral axis of the tube 37 The booster pin subassembly 97 is adjustedlaterally on the booster rod 516 to align the pin 98 on the desiredpredetermined neutral pivot assembly 28 when angle a equals 90.

axis. The pin subassembly 97 thus is positioned to strike the arm 66 ata point measured the distance X along the extended neutral axis i am aconstruction line perpendicular to the longitudinal centerline of themachine passing through the center of the support ring 73 of the By theoffset positioning of the pin 98 with respect to the booster rod 46 andthe mandrel rod 36, the neutral axis of the tube 37 is moved away fromthe tube centerline, since the distance the booster rod 46 travels andthe are distance C through which the bending form 51 rotates is governedby the position along the arm 66 which is contacted by the pin 98.

The instant machine is capable of performing bending of tubes of varioussizes without the substitution of machine elements as has been thepractice herebefore. In other words, the booster cylinders 33, 34 andthe mandrel cylinder 35 are adjusted laterally on the machine by themounting provided as discussed hereinbefore, thereby making it possibleto align the booster rod 46 and the mandrel rod 36 on the centerline ofeach size of tubing desired to be bent. The lateral shifting of the pin98 onto a neutral axis by means of the slide provided by the pinassembly 97, causes the coaction between the drive assembly 31 and thebooster assembly 27 to be related to the position of the neutral axisdesired. inasmuch as the booster rod 46 is aligned at all times on thecenterline of tubing to be bent, the setting of pin 98 on the desiredneutral axis the distance X, which is the arc distance C measured on theneutral axis, determines the desired distance of travel of the boosterrod 46 to accomplish a bent tube having walls at the bent portion ofrequired thicknesses. The machine 23 is designed such that the attitudeassumed by the arm 66 upon completion of a 90-degree bend is when thedistance L is equal to zero. These dimensions are factors incorporatedin computation of the proper dis tance Y at which the pin assembly 97 isto be attached to the booster rod 46 for a given tube size and neutralaxis. These computations are explained in detail in my Patent No.2,837,137.

The present invention provides mechanism for bending tubes, such as waveguides, in an accurate and posrtrve manner such that bends inlightweight ductile material may be made with precision. The bendingoperation is controlled automatically to etfect a bend in a tube withoutthe customary extreme thinning of the outer wall of a tube.

Obviously, many modifications and variations of the present inventionare possible in the light of the above teachings. It is therefore to beunderstood that the invention may be practiced otherwise than asspecifically described.

What is claimed is:

l. A tube bending machine which comprises a rotatable bending form,drive means coupled to the form for rotating the form, linkage meansattached to the drive means and pivoted by the movement of the drivemeans, booster means for applying pressure onto a tube toward thebending form and cooperatively engageable with the linkage means, powermeans for moving the booster means, and means responsive to thecooperative engagement of the booster means with the linkage means forcontrolling the drive means and the power means such that apredetermined relationship exists between the advancement of a tube andthe rotation of the bending form.

2. A tube bending machine which comprises a rotatable bending form,clamp means for holding a tube against the form; drive means coupled tothe form for rotating the form; pivot means including a pivot member andan arm supported intermediate its ends on the pivot member, one end ofthe arm being connected to the drive means for simultaneous pivoting ofthe arm and the pivot member responsive to operation of the drive means;booster means for applying pressure onto a tube and for feeding a tubeaxially toward the bending form and engageable with the other end of thearm of the pivot means; power means for moving the booster means; andcontrol means responsive to the engagement of the booster means with thearm of the pivot means for controlling the driving operation of thedrive means and the operation of the booster power means such that apredetermined relationship between the advancement of a tube toward thebending form and the rotation of the bending form is efiected.

3. A tube bending machine which comprises a rotatable bending form;clamp means for holding a tube against the form; drive means including amember movable in an axial path coupled to the bending form for rotationthereof; pivot means including a pivot member and an arm supportedintermediate its ends on the pivot member, one end of the arm beingconnected pivotally to the axially movable member of the drive means forpivotal movement responsive to translatory movement of the drive meansmember; booster means for applying pressure onto a tube and for feedinga tube axially toward the bending form and engageable with the other endof the arm of the pivot means; power means for moving the booster means;and control means responsive to the engagement of the booster means withthe arm of the pivot means for controlling the driving operation of thedrive means and the operation of the power means such that apredetermined relationship between the advancement of a tube toward thebending form and the rotation of the bending form is effected.

4. A tube bending machine which comprises a rotatable bending form;clamp means for holding a tube against the form; drive means including amember movable in an axial path coupled to the bending form for rotationthereof; pivot means including a pivot member and an arm supportedintermediate its ends on the pivot member, one end of the arm beingconnected pivotally to the axially movable member of the drive means forpivotal movement responsive to translatory movement of the drive meansmember; booster means for applying pressure onto a tube end for feedinga tube axially toward the bending form and including a pin assemblycarried by the booster means, said pin assembly being engageable withthe other end of the arm of the pivot means; power means for moving thebooster means, and control means responsive to the engagement of the pinassembly with the arm of the pivot means for controlling the drivingoperation of the drive means and the operation of the power means suchthat a predetermined relationship between the advancement of a tubetoward the bending form and the rotation of the bending form isefiected.

5. A tube bending machine which comprises a rotatable bending form;clamp means for holding a tube against the form; drive means including amember movable in an axial path coupled to the bending form for rotationthereof; pivot means including a pivot member and an arm supportedintermediate its ends on the pivot member, a clamp having a contouredface and supported on said arm, one end of the arm being connectedpivotally to the axially movable member of the drive means for pivotalmovement responsive to translatory movement of the drive means member;booster means for applying pressure onto a tube and for feeding a tubeaxially toward the bending form and including a pin assembly carried bythe booster means, said pin assembly being engageable with the contouredface of the clamp on the arm of the pivot means; power means for movingthe booster means; and control means responsive to the engagement of thepin assembly with the clamp for controlling the driving operation of thedrive means and the operation of the power means with the feeding actionsuch that a predetermined relationship between the advancement of a tubetoward the bending form and the rotation of the bending form iseffected.

6. A tube bending machine which comprises a rotatabl bending form; clampmeans for holding a tube against the 11 form; drive means including amember movable in an axial path coupled to-the bending form for rotationthereof; pivot means including a pivot member and an arm supportedintermediate its ends on the pivot member for pivotal and reciprocalmovement, one end of the arm being connected pivotally to the axiallymovable member of the drive means for pivotal movement responsive totransglatory movement of the drive means member; booster means forapplying pressure onto a tube and for feeding a tube axially toward thebending form and including a pin assembly carried by the booster means,said pin assembly being engageable with the arm of the pivot means;power means for moving the booster means; and control means responsiveto the engagement of the pin assembly with the arm for controlling thedriving operation of the drive means and the operation of the powermeans such that a predetermined relationship between the advancement ofa tube toward the bending form and the rotation V of the bending form iseffected.

7. A tube bending machine which comprises a rotatable bending form;clamp means for holding a tube against the form; drive means including amember movable in an axial path coupled to the bending form for rotationthereof; pivot means including a pivot member and an arm supportedintermediate its ends on the pivot member for pivotal and reciprocalmovement, one end of the arm being connected pivotally to the axiallymovable member of the drive means for pivotal movement responsive totranslatory movement of the drive means member; booster means includinga tube engaging rod; power means connected to the rod for movementthereof axially toward and away from the bending form; a pin assemblysecured to the rod engageable with the arm of the pivot means,

and control means responsive to the engagement of the pin assembly withthe arm for controlling the driving operation of the drive means and theoperation of the power means such that a predetermined relationshipbetween the advancement of a tube toward the bending form and therotation of the bending form is effected.

8. A tube bending machine which comprises a rotatable bending form;clamp means for holding a tube against the form; drive means including apower-operated cylinder having piston means movable in an axial pathtoward and away from the bending form and means connecting the pistonmeans with the bending form for rotation of the form by axial movementof the piston means; pivot means including a pivot member and an armsupported intermediate its ends on the pivot member for pivotal andreciprocal movement, one end of the arm being connected pivotally to thepiston means of the drive means for pivotal movement of the armresponsive to translatory movement of the piston means; booster meansincluding a tube engaging rod; a power-operated cylinder having pistonmeans connected to the rod for movement thereof toward and away from thebending form; a pin assembly secured to the rod engageable with the armof the pivot means; and a control valve responsive to the engagement ofthe pin assembly with the arm and in communication with the drive meanscylinder and the booster cylinder for controlling the driving operationof the drive means and the operation of the power means such that apredetermined relationship between the advancement of a tube toward thebending form and the rotation of the bending form is effected.

9. A tube bending machine which comprises a rotatable *bending form; apower source; power-operated clamp means for holding a tube against theform; means communicating the power source with the clamp means foroperation thereof; a power-operated mandrel means operatively connectedto the power source and including a mandrel trod movable by the mandrelmeans axially toward and away from the form for inserting and retractingthe mandrel into a tube held against the form; a power-operated boostermeans operatively conected to said power source and including a tubeengaging booster rod movable toward and away from the form by thebooster means for selectively feeding a tube axially toward the bendingform, and a pin assembly clampingly secured to the booster rod formovement therewith; valve means in communication with the power source,the booster eans, and the mandrel means for sequentially operating themandrel'means and the booster means; drive means including apower-operated means axially movable and coupled to the bending form forrotation thereof; pivot means including a pivot member fixed in locationwith respect to the bending form, an arm supportingly attachedintermediate its ends to the pivot member for pivotal movement about anaxis parallel to the axis of rotation of the bending form and formovement axially toward and away from the bending form, said arm beingconnected pivot-ally at one end to the power-operated means of the drivemeans and responsive to axial movement thereof to pivot the arm on thepivot member, the vpin assembly being engageable with the arm at aposition opposite the pivotal connection of the arm to thepower-operated means for imparting translatory movement of the armwithin the pivot member of the arm; a control valve in contactingoperative engagement with the arm, the valve being actuable bytranslatory movement of the arm and in communication with thepower-operated booster' means, the power-operated means of the drivemeans, and the power source to correlate the operation of thepoweroperated booster and drive means.

10. In a tube bending machine having a rotatable bendingform to which atube is clamped for bending, drive means for rotating the form, mandrelmeans for inserting and retracting a mandrel into a tube clamped to theform for bending, means for aligning the mandrel means coaxially with atube in position for bending, urging means for forcing the tube axiallytoward the form, laterally adjustable contact means carried by theurging means at a preselected point, pivotal and translatory meansconnecting the drive means and the contact means, control means engagedwith the connecting means responsive to translatory movement thereof,and hydraulic circuitry connected operatively to the control means, thedrive means, and the urging means for correlating the advance of theurging means with the rotation of the form by the drive means.

11. A tube bending machine comprising a rotatable bending form, drivemeans connected to the form for rotation thereof, pivotal andtranslatory means, an arm connected intermediate its ends to the pivotaland translatory means, booster means for urging a tube toward the formcoaxially with the longitudinal axis of the booster means, a contactmember attached to the booster means for axial movement therewith andadjustable laterally with respect to the longitudinal axis of thebooster means, means for adjusting the booster means coaxially with atube clamped to the bending form, one end of the'arm being attachedpivotally to the drive means for pivotal action about the privotal andtranslatory means responsive to translation of the drive means, theother end of the arm disposed in the path of the axial movement of thecontact member, the arm and the pivotal and translatory means beingtranslated in response to engagement of the arm with the contact means,valve means responsive to translation of the pivotal and translatorymeans, and means responsive to the valve means for operating the drivemeans and the booster means in a predetermined sequence whereby thespeed of rotation of the form is correlated to the speed of urging thetube by the booster means.

12. A tube bending machine which comprises a bending form, clamps forretaining a tube against the form for bending the tube upon rotation ofthe form, means for rotating the form, boosting means for urging a tubeclamped to the form axially toward the form, an arm connected at one endpivotallyto the rotating means for movement axially therewith, a contactmember connected to the boosting means for axial movement therewith anddisposed to intermittently engage the arm, control means responsive tothe contact of the arm by the member for correlating the operation ofthe boosting means and the drive means, and a pivot assembly attachedintermediate the ends of the arms for pivoting the arm responsive toaxial movement of the rotating means whereby the arm is disengaged fromthe contact member and for translation responsive to the engagement ofthe contact member with the arm for actuating the control means, saidpivot assembly including a mount, a bearing positioned concentricallyWithin the mount in fixed contacting engagemet therewith, rotatablemeans having an elongated aperture formed therethrough supported forrotation within the bearing, a lower plate underlying the mount andbelow the rotatable means, the lower plate having an upstanding centralportion of the configuration of the aperture of the rotatable means butof lesser length than the elongated aperture, the central portion of thelower plate being receivable slidably within the elongated aperture ofthe rotatable means and extending beyond the upper surface of therotatable means, an upper plate overlying the mount attached to theupstanding portion of the lower plate, and roller means supported by theupper and the lower plates in contacting engagement with the mountwhereby the upper and the lower plates may translate within the 14aperture of the rotatable means a limited amount and rotate with therotatable means within the bearing.

13. In a bending apparatus, means for gripping an article, a pair ofmovably mounted bending dies for holding a section of the article, meansfor moving the bending dies relative to the gripping means to bend thearticle, means for applying a force to compress the article in the diesduring the movement of the bending dies, selectively operable means forincreasing the effect of the force applying means, and means responsiveto a predetermined degree of relative movement between said bending diemoving means and said force applying means for operating saidselectively operable means.

References Cited in the file of this patent UNITED STATES PATENTS2,357,873 Bower .Q Sept. 12, 1944 2,571,400 Williams Oct. 16, 19512,611,659 Hadley Sept. 23, 1952 2,617,691 Bechler Nov. 11, 19522,792,048 Fuchs May 14, 1957 2,810,422 Bower Oct. 22, 1957 2,837,137Fuchs June 3, 1958

